Part 2: Tools of Recombinant DNA Technology (25 MCQs)
Part 2: Tools of Recombinant DNA Technology – Restriction Enzymes, Ligases, Polymerases (25 MCQs)
Q26. The most important tools of recombinant DNA technology are:
a) Restriction enzymes, ligases, vectors, host
b) Hormones and vitamins
c) Carbohydrates and proteins
d) Lipids and nucleotides
Answer: a
- a) Correct: Core tools = restriction enzymes, ligases, vectors, host cells.
Q27. The first restriction endonuclease discovered was:
a) EcoRI
b) HindII
c) BamHI
d) Taq polymerase
Answer: b
- b) Correct: HindII (1968) was the first discovered.
Q28. Restriction enzymes are also known as:
a) Genetic scissors
b) Molecular scalpels
c) Endonucleases
d) All of the above
Answer: d
- d) Correct: Restriction enzymes = molecular scissors, cut DNA at specific sites.
Q29. Restriction enzymes recognize:
a) Random DNA sequences
b) Specific palindromic sequences
c) Only RNA sequences
d) Any AT-rich region
Answer: b
- b) Correct: They cut DNA at specific palindromic sequences (same forward & backward).
Q30. Palindromic sequences in DNA are:
a) Same on both strands when read in 5’→3’ direction
b) Same on one strand only
c) Always GC-rich regions
d) Random sequences
Answer: a
- a) Correct: Palindromes read the same in opposite strands (5’→3’).
Q31. EcoRI recognizes the sequence:
a) GAATTC
b) AAGCTT
c) GGATCC
d) CCTGCAG
Answer: a
- a) Correct: EcoRI cuts at GAATTC between G and A.
Q32. HindIII recognizes the sequence:
a) AAGCTT
b) GAATTC
c) GGATCC
d) ATGCAT
Answer: a
- a) Correct: HindIII cuts AAGCTT.
Q33. BamHI recognizes:
a) GGATCC
b) GAATTC
c) AAGCTT
d) CTGCAG
Answer: a
- a) Correct: BamHI cuts GGATCC.
Q34. Which enzyme joins DNA fragments?
a) Restriction enzyme
b) DNA ligase
c) DNA polymerase
d) RNA polymerase
Answer: b
- b) Correct: DNA ligase seals gaps by forming phosphodiester bonds.
Q35. Sticky ends are produced by:
a) Restriction endonucleases with staggered cuts
b) DNA ligase
c) Endonucleases with blunt cuts
d) Exonucleases
Answer: a
- a) Correct: Staggered cuts → overhanging single-stranded sticky ends.
Q36. Blunt ends are generated by:
a) EcoRI
b) SmaI
c) BamHI
d) HindIII
Answer: b
- b) Correct: SmaI → blunt ends (no overhang).
Q37. Which of the following is NOT a restriction enzyme?
a) EcoRI
b) Taq polymerase
c) HindIII
d) BamHI
Answer: b
- b) Correct: Taq polymerase = thermostable DNA polymerase, not RE.
Q38. The enzyme used to amplify DNA in PCR is:
a) DNA ligase
b) RNA polymerase
c) Taq polymerase
d) HindII
Answer: c
- c) Correct: Taq polymerase from Thermus aquaticus → thermostable enzyme.
Q39. Function of reverse transcriptase is:
a) DNA → RNA
b) RNA → DNA
c) DNA → Protein
d) RNA → Protein
Answer: b
- b) Correct: Reverse transcriptase synthesizes DNA from RNA template.
Q40. Which enzyme is known as “molecular glue”?
a) Restriction endonuclease
b) DNA ligase
c) RNA polymerase
d) DNase
Answer: b
- b) Correct: Ligase joins DNA ends → molecular glue.
Q41. Restriction enzymes are naturally present in bacteria to:
a) Degrade bacterial DNA
b) Cut foreign DNA (e.g., bacteriophages)
c) Replicate DNA
d) Produce proteins
Answer: b
- b) Correct: They protect bacteria by cutting invading viral DNA.
Q42. Which enzyme is required to introduce foreign DNA into plasmids?
a) DNA ligase
b) Restriction enzyme
c) Both a and b
d) None
Answer: c
- c) Correct: RE cuts DNA, ligase joins it into plasmid.
Q43. DNA polymerases are required in rDNA technology for:
a) Synthesizing complementary strands
b) Repairing gaps
c) PCR amplification
d) All of the above
Answer: d
- d) Correct: DNA polymerases perform multiple functions.
Q44. Which enzyme protects DNA from degradation by restriction enzymes?
a) Methylase
b) DNA ligase
c) Helicase
d) Polymerase
Answer: a
- a) Correct: Methylases add methyl groups to host DNA → protection.
Q45. Type II restriction enzymes are important because:
a) They cut DNA at specific recognition sequences
b) They cut randomly
c) They produce proteins
d) They destroy plasmids
Answer: a
- a) Correct: Type II RE cut DNA at specific palindromic sequences.
Q46. Which type of cut is preferred in cloning?
a) Blunt end
b) Sticky end
c) Random cut
d) None
Answer: b
- b) Correct: Sticky ends → easy complementary base pairing.
Q47. Which enzyme is used in producing cDNA libraries?
a) Reverse transcriptase
b) DNA ligase
c) Taq polymerase
d) Helicase
Answer: a
- a) Correct: Reverse transcriptase converts mRNA → cDNA.
Q48. Restriction enzymes cut DNA by breaking:
a) Hydrogen bonds between bases
b) Phosphodiester bonds in backbone
c) Both a and b
d) Peptide bonds
Answer: b
- b) Correct: Restriction enzymes cleave phosphodiester bonds.
Q49. Exonucleases differ from endonucleases in that:
a) Exonucleases cut within DNA
b) Exonucleases cut at terminal ends
c) Both cut randomly
d) None
Answer: b
- b) Correct: Exonucleases remove nucleotides from ends; endonucleases cut internally.
Q50. The enzyme that seals nicks in sugar-phosphate backbone is:
a) Restriction endonuclease
b) DNA ligase
c) Helicase
d) DNA polymerase
Answer: b
- b) Correct: DNA ligase → seals breaks in DNA backbone.
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